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Know your daily intake, from A to zinc

December 04, 2006|Emily Sohn, Susan Brink

Vitamin by vitamin, here's what you need, according to the Institute of Medicine's Dietary Reference Intakes (DRIs, formerly known as Recommended Daily Allowances). Numbers are different for children, the elderly and pregnant and lactating women.

Vitamin A: It comes in two forms. Retinol, found in egg yolks, dairy foods and meat, is used immediately by the body. Beta carotene, found in yellow, orange and green leafy vegetables, is converted to vitamin A in the body. Vitamin A enhances vision, strengthens bones, teeth and skin. Recommended daily intake of 700 micrograms for women, 900 for men (3,000 international units, or IU). Too much vitamin A is highly toxic -- regularly taking more than 10,000 IU a day can cause nerve and liver damage, dry lips and nails, hair loss and might increase the risk of bone fractures.

The three Bs -- B6, B12 and folic acid: Studies show that B vitamins might help prevent heart disease and some cancers. All three help us build new proteins and folate helps synthesis of DNA. B12 works with folate to maintain the nervous system. Too little folate is a major cause of neural tube birth defects, such as spina bifida. All women of childbearing age should take a folate supplement. Folate may also lower the risk of breast cancer in women who drink alcohol. The recommended amounts are likely to change in the next few years as results come in from ongoing long-term studies, and a debate still rages between groups such as the March of Dimes, which believes food fortification with folic acid should increase in order to reduce the incidence of birth defects, and others who say not enough is known about effects on the overall population. For example, some early studies suggest that folic acid may stimulate the early stages of prostate and colon cancer. "There's an urgent need for more information," says Cornelia Ulrich, a nutritional scientist at the Fred Hutchinson Cancer Research Center in Seattle. Current recommended intakes are: 1.3 milligrams of B6, 2.4 micrograms of B12 and 400 micrograms of folic acid.

For The Record
Los Angeles Times Thursday December 07, 2006 Home Edition Main News Part A Page 2 National Desk 2 inches; 96 words Type of Material: Correction
Vitamins: An article in Monday's Health section on our requirements of vitamins and minerals described low levels of iron as anemia. In fact, anemia is a lower-than-normal number of healthy red blood cells. One of its causes is iron deficiency. The article also said that vitamin K supplements are recommended for people who take anticoagulants. In fact, since vitamin K is essential in blood clot formation, it's important that people taking anticoagulants work with their physicians to keep their vitamin K intake consistent. Sudden increases or decreases can interfere with the effect of the blood-thinning drugs.
For The Record
Los Angeles Times Monday December 11, 2006 Home Edition Health Part F Page 5 Features Desk 3 inches; 102 words Type of Material: Correction
Vitamins: A Dec. 4 Health section article on our daily requirements of vitamins and minerals described low levels of iron as anemia. In fact, anemia is defined as a lower-than-normal number of healthy red blood cells. One of its causes is iron deficiency. The article also said that vitamin K supplements are recommended for people who take anticoagulants. In fact, since vitamin K is essential in blood clot formation, it's important that people taking anticoagulants work with their physicians to keep their vitamin K intake consistent. Sudden increases or decreases in the vitamin can interfere with the effect of the blood-thinning drugs.

The other Bs -- thiamin (B1), riboflavin (B2) and niacin (B3): Thiamin, riboflavin and niacin work together with other B complex vitamins to help turn food into energy. These vitamins also help sustain the nervous system, skin and digestive tract. Low thiamin levels can result in difficulty concentrating, depression and muscle weakness. (Alcoholics are often severely low in thiamin.) Riboflavin works as an antioxidant and deficiencies have been associated with migraines, cataracts and arthritis. Niacin improves circulation and lowers cholesterol levels in the blood. The DRIs are 1.2 milligrams for thiamin, 1.2 milligrams for riboflavin and 15 milligrams for niacin. (These are averages for men and women.)

Vitamin C: Vitamin C has been on the public radar for a long time as an immune system enhancer and cold-fighter. It works as an antioxidant and helps build collagen (necessary for healthy bones, teeth and blood vessels). There has been a lot of debate about whether extra-large doses do any good -- and studies show no clear link between huge amounts of C and decreases in heart disease, cancer or eye problems. Because the vitamin is water soluble, you probably pee out anything beyond what your body can use. DRI: 75 milligrams for women, 90 for men, more for smokers. Citrus fruits, tomatoes, broccoli and spinach are good sources.

Vitamin D: This one has been getting lots of attention as accumulating studies show that vitamin D helps protect against some cancers, including breast, prostate and colon. It also helps with bone strength. Most people who live in northern latitudes become deficient in D during winter months. Current DRI is 5 micrograms (200 IU), but many experts think we need at least twice that much. Keep an eye open for news about this one. Vitamin D is fat-soluble and better absorbed when taken with food.

Vitamin E: Study results are mixed on whether vitamin E supplements can help reduce the risk of heart disease, and the American Heart Assn. refuses to recommend it. Large, long-term studies may help shed light on this question. One complicated thing about this fat-soluble vitamin is that it comes in eight forms, but our bodies absorb some better than others. "This highlights the challenges" of evaluating vitamins, says Brent Bauer, director of the Complementary and Integrative Medicine Program at the Mayo Clinic in Rochester, Minn. "Just because something works in the diet doesn't mean we can extract one part of it, take it in a pill and get the benefits." Look for "mixed tocopherol" on the label. Recommended intake is 15 milligrams (22.5 IU). Anything more than 1,000 milligrams (1,500 IU) could be toxic.

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